The invention to which this application relates is illumination means for articles where space is restricted, for example, but not necessarily limited to, in connection with touch-sensitive display panels.
Touch-sensitive applications are often used in connection with display panels and require a printed circuit board (PCB) to be mounted directly on the inside of a plastic fascia in order to allow the creation of touch-sensitive areas or buttons on the outside of the panel fascia. However, it can be problematic if these touch-sensitive buttons also require backlighting.
For example, Light Emitting Diodes (LEDs) cannot be mounted on the topside of the board, as the board is already touching the plastic, and there is not enough room for the LED between the PCB and fascia. A reverse through hole LED behind a hole in the PCB cannot be used, as the legs of the through hole LED would come through the board and foul the fascia plastic.
It is possible to drill a hole in the center of the button and use a reverse SMT LED to shine through the hole, but larger LEDS are needed to span the hole and such LEDs are costly due to their size. In addition, because the LED is close to the fascia, the light tends not to be distributed evenly; and there may be bright spots as the light from the LEDs is not diffused enough. These disadvantages are accentuated for larger regions were multiple LEDs are necessary, and the variations in light intensity become more apparent.
An aim of the present invention is to provide illumination for one or more regions of a touch-sensitive display panel which overcomes the above problems.